Teletypewriter system



Aug. 9, 1938. r. coRwlN Er AL TELETYPEWRITER SYSTEM.

Filed Sept. 28. 1935 ma x Rhoon l TLCRW/N INVENTORS B SSWEZEV EFW/1 TSON BV Wl YN A TTOR/VEV Patented Aug. 9, 1938 PATENT oFricsTELETYPEWRITER SYSTEM Thomas L. Corwin, Newark, N. J., Burdette s.Swezey, Floral Park, and Edward F. Watson, Larchmont; N. Y.: said Corwinassignor to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York: and said Swezey and said Watsonassirnors to American Telephone and Telegraph Company, a corporation ofNew York I Application September 28, 1935, Serial No.. 42,560

s claims.

'I'his invention relates to teletypewrlter systems and, moreparticularly. to arrangements for checking the accuracy of messagesperforated in tape while at the same time transmitting automaticallyfrom previously prepared tape without sacrificing any of the usualsupervisory vfeatures of teletypewrlter transmission.

In certain types of teletypewrlter service, it is desirable to check theaccuracy of certain messages. such as code messages or lists of ordernumbers, before transmitting them. 'I'his is because a mistake in asingle letter of a code word or a single figure of an order number mightchange the entire meaning of the word or the significance of the ordernumber.

Accordingly, it is an object of this invention to provide a convenientand practical arrangement for checking the accuracy of a message beforetransmitting it while also sending from other tape previouslyperforated.

It is also an object of this invention to enable an operator at astation, which is receiving messages from another station, to switch theteletypewrlter at the transmitting station from its local circuit to theline.

A further object of this invention is to enable an operator at astation, which is receiving messages irom another station having itsteletypewriter connected into a local circuit to switch thatteletypewrlter into the line circuit, during a pause in transmission, bymerely transmitting ordinary message signals and without transmitting aspecial break signal. n

These objects are accomplished by employing a special teletypevvriterset which can rapidly perforate tape used for operating atransmitterdistributor. The accuracy of the messages perforated on thetape may be checked, before the messages are transmitted out over theline, by two methods. The first method comprises simultaneouslyperforating the tape and printing only a local home copy by means of theselecting mechanism of only the teletypewriter at that station. Ill'heother method consists of first perforating the tape and then sending itthrough the transmitter-distributor over a local circuit to only theteletypewriter at that station.

An operator at a'teletypewriter station which ls receiving messages froma second station, can transmit a break signal which will stop the secondstations transmitter-distributor, operate an alarm device at the secondstation, and automatically switch the second stations teletype- Writerfrom its local circuit, should it be connected therein, into the linecircuit. During a (Cl. IHS- 4) pause in transmission by a sendingstation, it is not necessary for an operator at a connected station totransmit a break signal in order to communicate with the first stationbecause the teletypewrlter at the first station will be automaticallyswitched from its local circuit, should it be connected therein, intothe line upon the reception of ordinary message signals transmitted fromthe second station.

These and other features of the invention will now be fully describedand explained with reference to the drawing in which:

Fig. 1 shows diagrammatically the general apparatus arrangement of ateletypewrlter lsystem embodying the features of this invention; and

Fig. 2 illustrates in detail the circuit diagram for the teletypewrltersystem shown in Fig. 1.

According to the arrangement shown in Fig. 1, transmitter tape i isperforated in the tape perforator 2 at station A and is then fed intothe transmitter 3 by means of feed holes 42 (Fig. 2) and a sprocketfeeding mechanism (not shown). The perforations 4 (Fig. 2) in tape loperate the transmitting contacts 5 (Fig. 2) to condition distributor 6for thev transmission of signals. The signal impulses originating indistributor 6 are sent through the control circuit 1 and then out overline conductor 8 to a second teletypewrlter station, such as centraloffice B. If desired, the signals are also sent from the control circuitl to the local teletypewrlter I0 to make a home copy of the messagessent to central oiiice B. lin the drawing, central oiiice B is shown tobe capable of sending messages over line conductor 9 to theteletypewrlter I0 at station A which is capable of both receiving andsending messages. It is to be understood that central olce B has been soshown for purposes of illustration but may be changed to a subscribersstation according to thc requirements of a particular system.

Now that the general arrangement of the apparatus employed in thisinvention has been described, the operation of the invention will bedescribed in detail with reference to Fig. 2 which shows the apparatusin its neutral condition: that is, with both stations unoperated.

To call the subscriber at station A, an operator at central oce B movesswitch Il to its lower position to apply ringing current from alternatori2 to line conductor 8 and then to station A. At station A, the ringingcurrent passes over the top armature of unoperated relay I3, throughcondenser it, ringer i5, and then to ground. Ringer i5 will now operateto inform the subscriber at station A that he is being called.

In answering the call tromicentral ofiice B. the subscriber at station Amoves switch Il to its call-answer position at the left and also closespower switch |`|l for operating motor-generator Il and motor from powersupply source Il. when the motor-generator il is started, current enses,or man le. over conductor is. through relay il. and then to the negativeterminal of motor -lenerator Il. Relay i8 is now energized' operates itsarmatures to disconnect ringer connecting the printer equipment latstation A 'ro muuu s can, the mmr'ibern maan afollowsthesameprocedureasinansweringacall and operates switch II to itscall-answer" posil porforator switch 22. This closes a path from thepositive terminal of motor-generator Il through perforator switch 22 toJunction 2l. vll'rom junc tion 2! there are two paths: one leads throughrelay 2l to the negative terminal of motor-generator Il, the other pathgoes through the dis` tributor start magnet 2l and upper top armature ofimoperated break relay 2l to the negative terminal of motor-generatorIl. Current from motor-generator I0 now energises relays 24 and 2l. Uponbeing energiled, relay 2l operates its amature 2'I- thereby releasingdistributor brush 2l for rotation to transmit signal impulses.

Relayuinbeingoperatedatthistimewould close a path for positive currentfrom motorgenerator il to pass along conductor 42 over the ar'mature ofoperated relay 24, through relay 2l, armature of relay Il, right set ofcontacts oi' break key Il, break contacts l2, and then to the negativeterminal of motor-generator Il but for the fact that the break contacts82 are normally open, due to the rotation of cam 8| mounted on shaft 4l,when the contact of relay Slisclosedand are normally closedonlydurlng apart of the sixth pulse of a signal combination at which time thecontact of relay il is opened. eneeptwhen abreakaisnalistnnsmittedaswillbe explained hereinafter.

communication may now take place with perforations I in tape controllingtransmitting contacts i for causing distributor 0 to transmit signalimpulses, corresponding to the signals perforated in tape I, out overthe line circuit to central oiiice B. At the 'same time, these signalimpulses pass through the subscribers receiving magnet 8l for making ahome copy of the outgoing message.

In the event that it is desired tosend from the tape i without making ahome copy of the messages transmitted, the operator moves switch Il toits middle position. This opens the ener-Iiromthelineandtoprepareacircuitfor4 gising path for relay 2|. As aresult, the subscribers teletypewriter III is disconnected from the linecircuit and is connected into a local circuit leading from the positiveterminal of motorgenerator It. over conductor Il, lower top contact -oioperated relay I3, upper top armature of non-operated relay 2|,receiving magnet Il. sending contacts Il, break key Il, bottom armatureof non-operated relay 2l, and then to the negative terminal ofmotor-generator Il. Transmitter distributor 0 can now send messages overthe line to central oi'iice B without causing a home copy to be made byteletypewriter Il.

While teletypewriter I0 is connected into this local circuit it may beused for further perforation of tape I with or without a home copyaccording to whether the perforator transmitter switch 22 is closed oropen.

During transmission by the subscriber at station A, relay 2l. which isconnected directly into the line circuit, will follow all the signalstransmitted, opening its contact when energized by the line current frombattery I1 at central oiilce B. Also, during this time, cam Il mountedon distributorshaft Il, will be constantly rotating because shaft iscontinuously driven by motor 4| through the usual friction clutch (notshown) during the period of communication. Cam Il is so mounted on shaftlil as to close the break contacts I2 during a portion of the -sixthpulse, or stop impulse, of each code combination transmitted. This is totest for a "bx-esk during each revolution because, if the line is openwhen contacts I2 close, a break" will be recorded through the contactsof relay Il. However, during normal transmission of signals, either thebreali contacts 'I2 or the contact of relay 2l will be open at alltimes.

If an operator at central oillce B, or any other connected station,sends a break signal while the subscriber at station A is transmittingfrom perforated tape with his switchv it in its middle position, thebreak signal will open the line circuit for the duration of one or twocharacters. During this opening of the line, relay Il will becomedeenergized and will close its amature contact. When break contacts I2close now due to the rotation of cam Il, a circuit will be closed forcurrent from the positive terminal of motorgenerator Il to pass overconductor 48, upper right set of contacts (now closed) of switch Il,upperleft set of contacts of switch Il, through relay 20,' contact andarmature of relay Il. right set of contacts of break key 2|, breakcontacts I2, and then to the negative terminal of motor-l generator Il.

. This serves to operate relay 20 which locks-up through its bottomarmature subject to the release of relay 2l. The operation of relay 2icloses a path for positive current from motorgenerator Il to pass alongconductor u, through the lower right set of contacts (now closed) ofswitch il, over the top armature of operated relay 2l, through breakrelay 2,.and then to the negative terminal of motor-generator Il. Breakrelay 2l now operates its three armatures and closes a path for positivecurrent from motorgenerator il to pass along conductor Il, through thelower right set of contacts (now closed) of switch il. operated lowertop armature of relay 2|. through relay 2|, and then tothe negativeterminal of motor-generator Il thereby energising relay 2|. Relay 2|, inoperating its bottom and upper top armatures. switches the localteletypewriter Il from its local circuit to the line 2,190,535 circuitfor receiving signals transmitted from station B.

In operating its upper top armature, break relay 28 opens the circuitthrough the transmitterdistributor st'art magnet 28 and causes it torelease its armature 21 which catches the distributor brush arm 28 toprevent it from rotating and transmitting signals. Relay 28 also closesa path for positive current from motorfgenerator I8 to pass alongconductor 35, through break lamp 38, upper top amature of relay 28, andthen to the negative terminal of motor-generator I8 thereby lightingbreak lamp 38-as a visible signal to the subscriber at station A thatthe operator at station B desires to communicate. At the same time thebottom armature oi relay 28 shortcircuits the sending contacts 33 andbreak key 34 of the local teletypewriter I0.

The break signal can be locally discontinued by moving switch I8 to its"call-answer position at the leit and by opening the perforator switch22. This opens the energizing circuit of relay 24 which releases itsarmature thereby opening the locking-up circuit of relay 29 whichreleases and `opens the energizing circuit for relay 28. Although relay28 releases, relay 2| remains energized over a path through the contactsof switch I6. Relay 29 cannot be operated again until both the contactsof relay 30 and the break contacts 32 are closed.

In the event that the operator at station A has transmitted a series ofmessages, he might wish to pause for a short interval of time whilegathering information for other messages. To eiect such a pause intransmission, the operator at station A merely opens the perforatorswitch 22, leaving the power switch I1 closed and the switch I6 in itsmiddle position. This opens the energizing circuit of the distributorstart magnet 25 while leaving relay I3 operated. Magnet 25 now releasesits armature 21 which catches the distributor brush 28 and stops it fromrotating. Since the distributor brush 28 is attached to the shaft 40,stoppage of brush 28 by armature 21 will stop shaft 4U and cam 39 fromrotating further by disengaging the usual friction clutch (not shown)employed with such transmitterdistributors. This leaves the distributorbrush 28 in engagement with lever 21, as is shown ln the drawing, andalso leaves cam 39 in a position `where it will close the break contacts32, as is also shown in the drawing. With the circuit in this condition.all that the operator at station B need dn to effect a break signal isto transmit ordinary message signals. Relay 30 will follow these messagesignals and, since with the usual permutation code employed the rst, orstart, impulse of a signal is always an open impulse, relay 30 will moveits armature to close its contact. This serves to operate relay 29which, as is described above, eiects the operation of break relay 26 andrelay 2|. Relay 2l, in operating its bottom and upper top armatures,switches the teletypewriter In into the line circuit for receiving themessage signals transmitted from station B. Thus, the operator atstation B can break station A Aand can convert the teletypewriter atstation A from a sending condition to a receiving condition withouttransmitting the usual break signal thereby obtaining a saving intransmission time.

If the subscriber at station A should be transmitting from perforatedtape with switch I6 in its call-answer" position at the left and withswitch 22 closed at the time when an operator at station B transmits abreak signal. the circuit operation is much the same as that `lustdescribed above except that relay 29 is now maintained locked-up over acircuit traced from the positive terminal oi' motor-generator Il, overconductor 42, operated armature of relay 24, through relay 2l. over theoperated bottom armature of relay 29, and then to the negative' terminalof motor-generator I8. As a result. lamp 98 and relays 2l and 28 willoperate. Since switch I8 is already in its call-answer position, allthat need be done to discontinue the break signal is to open theperiorator switch 22 which opens the locking-up circuit for relay 29 aswas described above.

It the operator at station A has switch I8 in its left ptsition and istransmitting from the keyboard with the perforator switch 22 opened,

a break signal transmitted from central office B will not now operaterelay 29. However, since the teletypewriter I is now connected into theline circuit, the opening of the line by the break' signal will causethe teletypewriter I0 to run open and no printing will take place forthe duration of the break signal. 'I'his will serve to indicate to thesubscriber at station A that the operator at the distant central officeB wishes to use the line.

When the subscriber at station A wishes to disconnect the stationequipment, he opens his power switch I1 thereby stopping motor 4I andmotor-generator I8 thereby effecting the release of the relays. vRelayI3 in releasing its armatures connects ringer I5 to line conductor 8 andgrounds line conductor 9. If the subscribers printing apparatus is to beused for another call shortly, switch I8 may be left in its call-answerposition at the left.

On the other hand, if the subscrbers printer y set is to be used onlocal circuits, such as for locally testing the equipment or perforatingtape for future calls, switch I6 may be put in its disconnect positionat the right. The subscriber then closes his power switch I1 whichstarts up his motor-generator I8 and motor 4I. However current frommotor-generator I8 will not energize relay I3 at this time because thelower right set of contacts of switch I6 are now open. Therefore, thesubscribers teletypewriter IIJ and distributor 6 will now be connectedin a local circuit extending from the positive terminal ofmotorgenerator I8, over conductor 35, middle top armature of unenergizedrelay I3, distributor 8,- relay 3i), left contacts of the break key 3l,conductor 44, lower top armature of relay I3, upper top armature ofunenergized relay 2i, receiving magnet 38, sending contacts 33, breakkey 34, bottom armature of relay 2i, and then to the negative terminalof motor-generator Ill. The subscriber can now perforate tape whilemaking a home copy or local transmission from the teletypewriterkeyboard or transmitter-distributor may now take place.

lin case the subscriber at station A wishes to send a break signal whilehe is receiving messages from central oce B, he uses the break key 3i ofthe subscriber set and not the break key :it in the teletypewriter Ill.When the subscriber set break key 3i is operated, the line circuit isopened at the left contacts of break key 3i. In addition, the energizingcircuit for relay 28 is opened at the riglnt` contacts of break key 3i.This prevents operation of break relay 28 and also prevents the lightingof break lamp 36 and operation of relay 2l thereby obviating extramanipuolswitohssllandllbetoretransmission abov'especiilc embodimenthasbeen debedinordertoillustratetheinventionanditistobeiinderstoodthatvariousmoditicationsan--ployingthepl'inciplesandfeaturescttheinvenrent variations: andinstrlnnentalities at the nrst switching the teletype- 'l'lki' t "lltmuon from itl local circuit inw tion a iirst teletypewriter stationhaving a teletypevriter convertible from a sending condition to areceiving condition and vice versa. a tape perforator-trannnitter. atransmitter-distributor. and a localcircuit leading from thepertoratortransmitter and through the transmitter-distributor to theteletypewriter at that station: a second teletypewriter station having ateletypewriter capable of both receiving and lending message signals tothe ilrst teletypewriter station; a ccmmunication line connecting thetvo stations for the tranlnission oi' llshicant current variations:means for enabling the transmitter-distributorl to transmit over theline while theperiorator-transmitterandtheteletrpevriterattheilrststation areavailable for peri'orating and checking tape in the local circuit, andmeans operating in response tothereceptionofabreaksignaltransmittedtrunthesecondstationiorautcmatically convesting the teletypewriter atthe iirst station from itssending condition toits receiving conditionand ios'switchingtheteletypewriteriromitslocalcircuit into the line.

3. A teletypevvritcr system having in combination a iirst teletypewriterstation having a teletype'riter, a tape pertorator-transmitter, atransmitter-distributor. and a local circuit leading from theperiorator-transmitter through the transmitter-distributor to theteletypewritsr at that station: a second teletypevritsr station having ateletypewriter capable oi both receiving and sending message signals tothe first teletypewriter station; a communication line connecting thetwo stations ior the transmission of signincant current variations andinstrumentalities ior enabling the perrorator-transmitter andtransmitterdistributor at the ilrst stationto transmit mss sages fromperforated tape to the teletypewriter at the second station while havingthe teletypewriter attbeiirststatio'n idleandinstantiyavailableforbeingswitchedintothelineinrespcmeto a breaksignal sent from the second station.

4. A teletypevn-iter system having in combination a iirst teletypewriterstation having a teletypevvriter convertible from a sending conditiontoareceivingconditionandviceversa.saidtele typewriter' having sendingcontacts. a second teletypewriter station having a teletypewriter. acommunication line connecting the two stations for the transmission otpermutation code signals. a normally open circuit for short-circuitingthe sending contacts o! the teletypewriter at the rst station. anormally unoperated instrumentality tor closing said normally opencircuit. and means for operating said normally unoperatedinstrumentality in response to the transmission over the communicationline by the teletypewriter at the second station of an ordinarypermutation codesignalduringapauseintransmissionbythe teletypewriter'atthe ilrst station.

5. A teletypewriter system having in combination a nrst teletypewriterstation having a teletypewriter, a tape pertorator-transmitter, atransmitter-distributor, a local circuit leading from theperforator-transmitter and through the transmitter-distributor to theteletypewriter at that station. a second teletypewriter station having ateletypewrlter capable of both receiving and sending message signals tothe ilrst teletypevriter station; a communication line connecting thetwo stations for the transmission oi signiilcant current variations; acircuit for converting the teletypewriter at the ilrst station from asending condition to a receiving condition; nrst control means forpreparing said circuit during a pauseintransmisaionbytheteletypewriterattheilrst station: and second controlmeans operating in response to ordinary message signals transmitted fromthe teletypewriter at the second station for completing said circuit.

